Influence of thermophilic lactic acid bacteria strains on propionibacteriagrowth and lactate consumption in an Emmental juice-like medium

Swiss-type cheeses such as Emmental are characterized by the successive dev elopment. of thermophilic lactic acid bacteria (TL,SB) and propionibacteria . The aim of this study was to determine whether the choice of TLAB strain influenced propionibacteria. TLAB and propionibacteria were cultured sequen tially under the conditions prevailing in cheese. First ly! 11 Emmental jui ce-like media were prepared by fermenting casein-enriched milli with pure o r mixed cultures of TLAB (Lactobacillus helveticus: Lb. delbrueckii subsp. lactis and Streptococcus thermophilus), differing in their proteolytic acti vities. TLAB cells were then removed by microfiltration. Finally, fire stra ins of Propionibacterium freudenreichii were grown on these media at 24 deg rees C under anaerobiosis and their growth characteristics and lactate cons umption determined. The media mainly differed in their contents of peptides (1.9-5.3 g/kg) and free amino acids (1.0-5.6 g/kg) and the proportions of lactate isomers (42-92 % of the L(+) isomer). Propionibacteria were signifi cantly (P < 0.05) influenced by TLAB strains (differences in doubling times of up to 20 % and differences in lactate consumption after 600 h culture o f up to 52%). The influence of TLAB was similar for all the propionibacteri a tested, depended on the TLAB strains and could not be generalized to the TLAB species. Propionibacteria were stimulated by high peptide levels. lon levels of free amino acids and NaCl, a low proportion of L( +)-lactate and other undetermined factors. However, variations due to TLAB were less than those between propionibacteria strains.